1. Field of the Invention
The invention concerns a system of microwave transmit or receive antennas.
2. Description of the Prior Art
In some applications it is necessary to transmit or to receive microwaves in more than one band. Antennas for one band of frequencies are generally not optimized for another band of frequencies. This is why one antenna is usually provided for each band of frequencies. However, this multiplication of the antennas gives rise to problems of overall size, in particular for space applications. To reduce the overall size the antennas can be disposed concentrically, with the central antenna being that for the highest frequencies.
The invention starts from the observation that the purity of the signals transmitted by a system of at least two concentric antennas is not always satisfactory and that the origin of the disturbance lies in the transmission of signals from the central antenna to the peripheral antenna.